LIGHTHOUSE. 260 LIGHTHOUSE. ment. It is claimed llial live gallons of iiiincral oil will ;.'ii' as much light as four gallons of lard oil, while mineral oil al the present writing costs about SY2 cents, and lard oil 37 cents per gallon. The highest price paid for mineral oil since the board commenced to use it in large quantities was :50 cents i)er gallon ; the lowest (iV4 cents. A certain class of lights are shown at the ends of long piers, which are often dan- gerous to reach in licavy weather, when they are swept by the waves and wind. For this ])ur- pose a burner has been invented on the constant- level principle, whidi will keep a light burning for six and even eight days ami nights without attention, so the light need only be visited in safe weather. Gas. The use of gas lias been atteni|)ted in a number of places. Accidents to the gas-pipes are most liable to occur in very bad weather, when repairs are most dilticult to make. Com- pressed gas supplied from tanks is in use for lighting buoys (q.v.) and inaccessible beacons. A combination gas-machine is used to furnish the light to some of the stations on the North- western lakes. This machine works automati- cally, making the gas from gasolene and fur- nishing a light which can burn, according to the size of the machine, from thirty to ninety days without attention. Elkctuic Light. E.|)priments with this il- luniinant have not been exhaustive, and it is by no means certain that electric lighting is gen- erally superior to the present system. In some places the intensity of the electric light has proved a detriment to its use, as was the case with the Hell Gate electric light. This tower, 2o5 feet high, was the tallest skeleton iron tower erected by the United States lighthouse service. It showed nine electric lights, each of 6000-candle power, and was designed to illuminate the nar- row, intricate, and dangerous channel. At night when lighted the eflect was grand, but the light was so brilliant that it dazzle<l the eyes of the pilots and prevented them from seeing objects l>eyond the circle illuminated, and the shadows thrown were so heavy that they took the form of obstacles. So the light was discontinued in ISSfi. at the instance of those who had obtained its establishment. Incandescent lights have been successfully used in the lighting of buoys. The British Government in 188.5 created a commission to report upon the relative merits of electricity, gas. and oil as lighthouse ilhnninants. The com- mission indicated that the electric light stands first in the rank of lighthouse illuminants during clear weather, if expense be no matter of con- sideration. The exact definition of the lighted area, and the total darkness beyond this area, however, jiroved a positive source of danger in the case of the Hell (iate light. Vi.siBiLiTY OF I.KiiiTS. The distance at which any light can be seen, of course, dejiends on the height of the tower and varies willi the state of the atmosphere. The greatest recorded distance at which an oil light has been visible is that of the holophotal light of Alleppi at Travancore. which has been seen from an elevated situation at a distance of 4.') nautical miles. The holophotal re- volving light at Raccnlieu. in Newfoundland, is seen every night in clear weather at Cape Spear. a distance of 40 nautical miles. The distance from which the principal lights can be seen is limited only by the horizon. It is deemed that 250 feet is the maxiiiiuiii height necessary or advisable to give a light; this gives a horizon 18 miles distant. This can be extended to about .'!!) miles by ascending to mast-head. When a light is unduly elevated, it is often obscured by clouds and fogs. Lighted Beacons and Buoys. For the illniiii- nation of beacons, where no light-keeper is on the spot, or of buoys comparatively near shore, elec- tricity is the most desirable agent to produce the light. The number of lighted luioys in the I'nited States is small, tlicre being but !)3, of which o4 are on the Great Lakes. Of these 82 are lighted with gas and 11 by electricity. The method of light- ing buoys and beacons at sea by gas and elec- tricity has already been alluded to in preceding paragraphs and under Bi'OY. Electric-light l)Uoys for the purpose of defining the main entrance to New York Harbor were first put in operation in November, 1888. Each of these carries an incandescent electric lamp operated by a cur rent generated on shore at Sandy Hook, with which each buoy is connected by a sulimarino cable. The lantern consists of a circular base and stout framework of brass, having curved panes of thick glass in the sides and segmental panes in the top with a ring at the top to serve as a handle. An incandescent electric lamp of 100- candle power has been in operation in the north beacon at Sandy Hook since August 10. 1SS9, the current being supplied from the generating sta- tion that operates the buoy lamps. During 180(5 similar lamps were established in the Samly Hook main light and in the South Hook beacon. Fog-Signals. A prominent feature of the lighthouse equipment of all countries is the fog- signals or sound signals used to guide mariners during fogg}' weather. See Fog-Sign.ls. Statistics. According to a compilation made by Mr. Arnold Burges .Johnson, chief clerk. United States Lighthouse Board, in 1889 the number of light stations in the different parts of the world was as follows: Europe 3,309 North America 1,329 Aula 476 Oceanlca , Africa s<jnt!i .merica.. West Iiulies 319 219 167 106 Total 5.925 The total number of lighthouses and other lighted aids to navigation in the United States in inOO was as follows: AIDS Is a. J r ■S s. 3"
Electric lifrlits 5 40 16 35 3 170 Hi 58 99 16 49 425 .■Jl 11 28 "18 1 5 "18 7 "is "3 5 58 20 23 1 63 Thrpe - and - a - half - order 8 1 11 Knurth-order Hp:bt8 95 283 Fifth-c)rder lights H ' 165 SWtli-order lights BO ' lOS 81 198 , 16 2 1 51 Post lanterns 118 109 1-396 ! 2.04R Litrlit-vpsselfl in position... Elpctrir-liphted bnoys 3 10 "64 44 11 82 Total lighted aids 1,100 188 479 1,396 3,163
